Find your own threshold
Can you tell the difference between MP3 and linear (PCM WAV/FLAC/lossless) audio? All depends on the encoding bitrate - personally, I don't reckon I could tell the difference between 320k MP3 and linear, but at 96k? Hell, yes.
Take a piece of music you know - if it's got a piano in it, so much the better - and encode it at all sorts of bitrates. Then listen to them vs. the uncompressed version: start at the horrible-sounding low bitrate ones, and see how far you need to go until you can't tell the difference.
At the commercial radio group I work for, we distribute our production audio uncompressed, and our broadcast streams internally as 384k MP2, or 345k aptX.